class Solution {
  public int numWaterBottles(int numBottles, int numExchange) {
    int ans = numBottles;

    int amount = numBottles / numExchange;

    while (amount != 0) {
      ans += amount;
      numBottles -= (numExchange - 1) * amount;
      amount = numBottles / numExchange;
    }

    return ans;
  }
}